Life in a few Drops of Water:Dinoflagellates

This is the third in the series of images of some of the organisms found in just a few drops of water collected from a pond in a disused quarry on the edge of the moors in Weardale

This little object (which I think may be a species of Peridinium), a mere five one hundredths of a millimetre across, is a dinoflagellate - a single-celled, hardshelled organism that's powered by two rapidly undulating flagellae. One runs on the horizontal groove around the 'equator' of the example you can see here. The other runs in vertical groove, extending from the equator to the apex - it's out of sight on the distal side of this image, although you can just see the apex of the vertical groove at the top. It seems like an unlikely means of motive power but it works - this one whizzed all over the slide before it paused for long enough for me to get a photograph.

This is the empty shell of a dead dinoflagellate, which reveals the intricate pattern on the armoured surface composed of cellulose plates. Unfortunately....

....it wasn't intact - you can see where about a quarter of the sphere has broken away, but you can also see the equatorial flagellar groove rather nicely. The green object approrach from lower right is a diatom, which is just about to punt the diatom out of the way as it glides past.

For some fascinating recent research on dinoflageelates, take a look at this post about a predatory dinoflagellate at Jennifer Frazer's The Artful Amoeba web site, where you can read about their amazing biology and also find links to drawings and electron micrographs that show the organism rather more clearly than my photographs.

Coming next: An assortment of protists

Life in a few Drops of Water: Desmids

This is the second in the series of images of some of the organisms found in just a few drops of water collected from a pond in a disused quarry on the edge of the moors in Weardale.

This is  a desmid - probably a species of Cosmarium. Desmids are typically constricted in the centre of the cell to form two mirror-image halves.

These are single-celled, photosynthetic algae that often have a patterned cell wall that's ...

.... most clearly visible after the cell has died and lost its chlorophyll.

This appears to be one half of a desmid that has broken at the bridge joining the two halves (known as the isthmus), revealing the fractured hole.

Coming next: Dinoflagellates

Life in a Few Drops of Water: Diatoms

A few days ago, when we were out walking in Weardale, I collected a small sample of water from a pond in a disused quarry on the edge of the moors, then spent several hours that same evening exploring just a few drops of the pond water - maybe ten in total - under the microscope. The organisms pictures in this post are all diatoms - minute photosynthetic organisms encased in a shell of pure silica that often bears the most intricate pattern on its surface. This one, caught in the act of dividing, is Pinnularia.

 

Some are long and thin (this is Nitzchia sigmoidea), while.....

....others are joined together in chains.

Navicula? When diatoms die their silica shell remains, almost indestructible, and in that transparent state, with no contents, the full beauty of the sculpturing on their shells can be appreciated.

The pattern of fine ridges on Cymbella tests the ability of microscope lenses to resolve such fine detail.

Diatoms generally move in a gliding motion through the water but sometimes they can be attached to a substrate via mucilaginous stalks.....

... seen here at higher magnification.

Most of these organisms are less than one twentieth of a millimetre long.

Coming next: Desmids....mirror-images in miniature